Dog is the dog (obviously) from The Storyteller, and is generally the only character who listens to The Storyteller's stories in person. Dog generally provides wisecracks and asides to the more serious storytelling. Like The Storyteller, he is rarely part of the actual story. In the first episode, "Hans, My Hedgehog," Dog as well as Stroyteller have roles as waiters in the story, and in "Sapsorrow," he appears to be among Sapsorrow's animal companions, and at one point confirms she's telling the truth when Sapsorrow tells her father that she wasn't taking the ring like her sisters had said. At the beginning of "The Soldier and Death," Dog wants to eat the biscuits that The Storyteller needs for his story, prompting Dog to let him tell the story (because the sooner the story ends, the sooner he can eat them). Although The Storyteller was replaced with a different actor for The Storyteller: Greek Myths, Dog reprised his role as the dog.

Outside of The Storyteller franchise, Dog was interviewed by Rowlf for Muppet Magazine, where he talked about how he met the Storyteller and revealed that although he lives with the Storyteller, he is not the characters (or anybody's) pet. Dog also made a few appearances (outside of The StoryTeller second half) on The Jim Henson Hour. In episode 103, he appears in Jim Henson's intro in place of the Lion. In "Secrets of the Muppets," he appears at the Creature Shop, where he reveals himself to be a member of the Organization of Muppet Dogs (and also reveals that there is an Organization of Muppet Dogs).

WHY DOES THE STORYTELLER NEED DOG?
The Storyteller needs Dog to provide some comic relief, to have SOMEBODY there to listen to his stories, and because the Dog is just plain awesome a character.